Sealing liquid and process of making same



Dec. 25, 1934. w. A. GRUSE SEALING LIQUID AND PROCESS OF MAKING SAME Filed Jul 29, 1952 Patented Dec. 25 1934 TED STAT SEALINGLIQUID-Algl) PRocsss-oF-MAKING- Williani A. Gruse Wilkinsbi rg', re; assignorto p v p GultRefiningCompany,'Pittsburgh;Pa, acor-' notation of Texas Application July 29, 1932, serial No; 626,180 i'l'oiaims. (ohms-149i" This invention relates" to sealing liquids and processes of making same; and it comprises a particular distilled petroleum 'oil adapted forms as a sealing liquid,1for example, in waterless gas holders, said oil being characterized by.v a specific gravity somewhat greater than water; by a; viscosity about that of a. medium-heavy'engine lubricating oil, by fluidity. at low temperatures, by a flash point not less than 300 F;, and by very low tendency to emulsify with, or otherwise carry: water, said oil usually being derived from a heavy residual tar resulting from the cracking: or socalled reforming of petroleum naphtha; and it also comprises a method of making such an oil wherein a heavy residual tar producedin crack ing and re-forming. alight distillatesuch as naphtha, is reduced by distillation to about-half its original volume, the residue being thenblended with a viscosity reducing material, or the last" mentioned residue is further distilled; usually under non-cracking conditions, to'producevariousdistillates, one such distillate having the'dee sired'properties being produced during such distillation; all as more fully'hereinafterset forth and as claimed. i

In the last few years the so-call'ed waterless gas holders have been gaining favor at the ex pense of older types, such1as the floating bell type to secure this a peripheral gutter or trough,'-kept" supplied with sealing liquid, is provided on the piston. A so-called rubbing plate, mounted on the piston, is held' pressed against the walls of the holder and a stripfof' canvas makes'aflexible connection between this rubbing plate and the outer edge of the "peripheral'gutterl The l gutter is kept filled with a sealing liquid; the level of which is maintained some distance abovethe top of the rubbing plateandcanvas strip. Theseal ing liquid forms the actual seal liquid drains downwardly between the rubbing 'plate and the side of the holder to some extent; Water" 50'.

condenses on the inner wall: of the-holder and gets mixed with the sealing: liquid; Bymakingt the sealing. liquid heavier than water ibis? pussieble to conveniently" and automatically "separate the condensed water from the: sealing liquid andi also keep: water from accumulating?in the guttem and rotting the canvas. The sealing liquid must also be substantially insoluble in. water and not readily emulsifiable. With a heavy liquid of this. character, anyirain water, etc. gaining access to the top of the gas holder floats on the seal and can bedrawn off by extremely: simple and auto maticmeans: H

Theselectionbfa suitable sealing. liquid presen'ts many difliculties and: no wholly satisfactory solutiomof the" problem. has in. the past been attained; Wateralone is unsatisfactory in that it causes rotting oi canyasand rusting. of metal. lfiitshouldz'freeze and so secure the piston to the holderrollss total destruction might result. Coal tar and'vari'ous heavy coal tar distillates have beentried. Straight'coal. tar and straight coal tar distillates have a tendency to emulsify. with water and are lost? in considerable quantity in the condensed waterwhich is drawn off and discarded; and they have'many other impractical aspects. q a

. Arliquid suitable for use in the seal should be ofasspecificgravity greater than that of waterybe capable of flowing at all ordinary atmospheric;- temperatures and 1 advantageously at temperatures as lowas', sayi 20 F.; be substantially free from any unsaturated hydrocarhens and. volatile: compounds which can be absorbed byl the gas and. give a low flash point; be inert to air and gas;- and it should not emulsitywith wateror withdrip oil from the gas; it shouldnbtideposit sludge in use with water gas or coal gasand. it should not dissolve more than 1 per centof water.

' .Ordinarylcommer'cial oils made irompetroleum donot'pos'sess the combination of characteristics. required. In particular, it is difficult to find: any oil of high specific gravity with a sufilcient fluidity at low temperatures... Ordinary cracking stil'ltar's are'useless' for this purpose.

I have founcL however, that a drastic cracking of. certain lig'ht. petroleum oils such as naphtha tends to give residual tar products of. high spe-' cific gravityand low viscosity and. that certain oftsuch tars-can. beused as raw material for production of excellent sealing liquids. By

drastic cracking in this connection I mean subjection to extremely high temperatures, tempera-. turesrabove 900 to 925 for example.

The degree of cracking to which a given petrol'eum...oi1'can.be subjectedin commercial operation is: that which; it will stand without'excese sive .coke deposition, and most petroleum oils cracked at. highftemperatures produce tars car-- ryingclsan excessiveamount of solid material.

solid and their distillates possess excessive viscosities.

gasoline stocks; as in the operation commonly known as re-forming. Ifhave found that extremely desirable distillates for the present purpose can be recovered from these reforming-still tars. The tars produced in this particular cracking are characterized by high fluidity, by heavy gravity for a given boiling point range, by chemical and physical stability, and by freedom from constituents which become solid and separate out at ordinary temperatures;

In a specific embodiment of the present. invention making a sealingcil suitable for the described purposes, I took 100 parts of atar from v a pressure still in which naphtha had been subjected to a temperature of about 950 F. and a pressure of 1500 pounds per square inch. This tar was reduced, or topped, at atmospheric pressure until 40 parts came over as distillate. This was discarded. At the end of this distillation the temperature had risen to about 600 F. and. the specific gravity of the distillate approached 1. The remaining tar was then subjected to vacuum distillation under a pressure of somewhat less than 10 mm. absolute. Fifteen parts of distillate were recovered in a single out having a specific gravity at 60 F. of .1.001.and a viscosity of 50 seconds S. U. V. at. 100;F. Twenty parts more were then recovered as a out having a specific gravity of 1.05 and a viscosity of 410 seconds S. U. V. at 100 F. f The temperature in the still at this point had risen to 516 F.

; This last out or a mixture of the last two was suitable for use as sealing liquid.

- In methodical operation I usually distiloff about 40 to 50 per cent of the original volume.

vantageously maintained below about -600F. to;

avoid'cracking. The 5 per cent cuts recovered in this manner usually range in specific ggravity from about 1.0 to 1.05. Their viscosity usually increases towards the end of the distillation to a point somewhat-greater than that desired in a sealing liquid. However, the heavier of these5 per cent cuts are suitable as sealing liquids when blended with sufiicient material of low viscosity and high gravity to producea mixture of suitable viscosity. 7 The lighter and intermediate cuts are usually suitable without such blending.

The cuts may be blended among themselves:

The above procedure can be altered to afconsiderable extent without departing from the scope of my invention. In its broader aspects the process of my invention consists in taking a light petroleum distillate, subjecting said dis-' tillate to pressure still cracking conditions at temperatures above 900 925 F., recovering the (reforming-still) 1351 produced in said cracking step, distilling this tar, discarding the first-dis- I have found, however, that conditions are somewhat different in the case of tars pr"o"'" duced by a drastic cracking of. loWboilingp'etroleum distillates such as naphtha, kerosene andtillaterunning about 40 to 50 per cent by volumebecause of low density, and then either blending the tar bottoms with a viscosity reducing liquid or continuing distillation under noncracking conditions until from 40 to 25 per cent of the initial volume remains in the still, and recovering-the intermediate fractions. By noncracking conditions I mean that the distillation is conducted under reduced pressure or in .thepresence of steam or other similarly acting 'medium.

The secondarytar bottoms remaining after the described removal of 40-50 per cent of the reforming-still tar can be blended with various liquids'of high gravity to produce sealing liquids of specific viscosities. Such a viscosity reducing agent for this material may be one of the beforementioned 5 per cent distillate fractions from another batch or it may be an organic compound. Among such organic compounds there may be mentioned many halogenated compounds such as chlorinated naphthalene (halowax oils), chlorinated diphenyls, chlorinated fractions of coal tar oil or pressure still tar, and tributyrin, which latter is the butyric acid ester of glycerol. Reforming-still tar varies with the conditions of the .re-forming operation, but distillates can always be produced with characteristics of the kind-indicated by conducting the operation as herein described.

The distillation temperature while producing sealing liquid from reforming-still tar should not rise much above 600 F. If desired the distillate cuts from the tar can be subjected to common refining operations.

For a better understanding of the present invention in the accompanying illustration I have shown in some detail thetypeof gas holder in which sealing liquids made under the present invention are most advantageously employed. In the illustration there is shown more or less diagrammatically a structure of a waterless gas holder and of the gas seal.

Fig. 1 is a side elevation of a gas holder, part of this showing being in section, while Fig. 2 is an enlarged sectional view of the gas seal.

In the drawing like elements are designated by like numerals.

Thegas holder, asshcwn in Fig. 1 is formed of an outer shell 1, surmounted by a roof 2. The shell is-in the form of a polyhedral prism with 10 to 2801' more vertical sides depending upon the capacity of the holder. The only moving part of the holder is the so-called piston or diaphragm 3. This pistonis supported by the gas and by weighting it the gas pressure can be regulated in a simple manner. Around the periphery of the piston are placed two series of radial rollers 4 at different heights, the vertical distance between the two series being about one-tenth of the diameter of the holder. These rollers move along so-called rubbing strips, not shown, as the piston rises or falls.

, The structure of the gas seal is shown in section in Fig. 2. Around the periphery of the piston and at the bottom is a trough or tar cup 14 which forms the, gas seal. The mechanical structure of the seal includes a rubbing plate or bar 5, which at the bottom is attached to the piston proper by a strip of canvas 6. The canvas is attached to the back of the rubbing plate and passes over a wood or metal spacing rod 7 which serves to prevent the canvas from coming into contact :with the'side of the holder. The canvas strip 6 is attached to the piston 3 by means of a wooden strip 8 which is bolted to a peripheral flange 8.

The rubbing plate is usually made of metal sufficiently thin and flexible to accommodate itself to any slight irregularities in the surface and is kept pressed against the side of the holder by a'lever 10, mountedon the piston, thisbeing pivoted at 11 and weighted at 12. The troughlike depression 14 formed between the side of the holder and the piston is filled with a sealing fluid 13 which serves to prevent the escape of gas. sealing liquid past the joint formed between the rubbing plate and theside of the holder. This liquid is recovered in a sump 15 at the bottom of the holder, water is separated therefrom by gravity and the liquid is then pumped back into the trough. Thelevel of the liquid in the trough is generally kept constant by automatic means connected to the sealing liquid pump. It is desirable to employ a sealing liquid having at 1 least some lubricating properties in order to keep the joint between the holder and the rub bing plate lubricated.

The sealing liquid produced by the process hereinbefore described unites the properties de sired in such a liquid in high degree. The product of my invention is a distillate having a specific gravity above 1.000, having a viscosity of not over 700-800 seconds S. U. V. at 100 F., having the characteristics of remaining fluid at temperatures of about 0 F. or lower, having but slight tendency to form emulsions with water, having a flash test of not less than 300 F., having low acidity and sulfur content and having a water content of not substantially over 1 per cent. While these properties make my product especially adapted to the waterless type of gas holder, the same properties make my product suitable for other types of holders as well. For example, a holder of the floating bell type can be supplied with the sealing liquid of the present invention with advantageous results.

As previously stated coal tar and certain coal tar distillates have been tried for the purpose for which my product is intended, but these materials have shortcomings. My product is miscible with these materials and obviously its mixture with any of them would greatly improve their usefulness. Beyond that I find that mixture of my product with these materials substantially lessens their tendency to emulsify. Without limitation to any particular blending material, blending permits production of sealing oils having specific combinations of particular characteristics.

What I claim is:

1. As a sealing liquid for waterless gas holders, a pressure still tar distillate obtained by the fractional distillation of the residual tar from the cracking of alow boiling petroleum oil having a specific gravity greater than that of water and a viscosity of the order of that of medium and heavy engine lubricating oils.

2. A gas holder sealing oil produced from the residual tar of a naphtha cracking process having a specific gravity of approximately 1.01 to 1.05,

a viscosity at 100 F. on the Saybolt universal viscosimeter of from 200 to 700 seconds, a flash point of not less than 300 F., and being substantially fluid at low temperatures.

3. As a sealing liquid for waterless gas holders, a naphtha cracking still tar distillate char- There is always a slight leakage of the acterized by a specific gravity greater than that of water, a viscosity at 100 F. of the order of medium and heavy engine lubricating .oils, having low sulfur content and acidity, having a water content of less than 1 per cent and having no strong tendency to emulsify with water.

4. As a new composition of matter, a blend of a pressure still tar distillate obtained by the fractional distillation of the residual tar from the cracking of a low boiling petroleum oil and a coal tar oil.

5. As a new composition of matter, a blend of the tar distillate of claim 3 with a coal tar oil.

6. In the manufacture of sealing liquids for waterless gas holders, the process which comprises subjecting a low boiling petroleum distillate to drastic cracking, recovering the tar formed during said cracking step, reducing said tar to a residuum by distilling off a substantial proportion, further distilling said residuum under non-cracking conditions and recovering a distillate having a specific gravity greater than 1.

7. The process of claim 6 in which the low boiling distillate employed is naphtha.

8. The process of claim 6 in which from to per cent of the tar is distilled off to produce said residuum.

9. The process of claim 6 in which said residuum is distilled under reduced pressure.

10. The process of claim 6 in which the temperature of the distillation steps is maintained below 600 F.

ll. In the manufacture of sealing liquids for waterless gas holders, the. process which comprises distilling a tar from a naphtha cracking still and recovering a fraction having a specific gravity greater than 1 and a viscosity of the order ofthat of medium and heavy engine oils.

12. In the manufacture of sealing liquids for waterless gas holders, the process which comprises drastically cracking a low boiling petroleum distillate, recovering the tar formed during said cracking, distilling said tar and recovering a fraction having a specific gravity greater than 1 and having the property of remaining fluid at low temperatures.

13. The process of claim 12 in which the tar is distilled under non-cracking conditions.

14. In the manufacture of sealing liquids for waterless gas holders, the process which com prises distilling a tar from a naphtha cracking still, rejecting a fraction lighter than water and recovering a fraction heavier than water.

15. In the manufacture of sealing liquids for waterless gas holders, the process which comprises reducing a tar from a naphtha cracking still -to a residuum representing from 50 to per cent by weight of the original tar, subjecting said residuum to vacuum distillation and recovering a fraction having a specific gravity greater than 1.

16. As a sealing liquid for gas holders, a reduced, re-forming still tar obtained from the cracking of a low boiling petroleum distillate diluted with an organic viscosity reducing liquid having a high gravity.

17. In the manufacture of sealing liquids for gas holders, the process which comprises reducing a re-forming still tar obtained from the cracking of a low boiling petroleum distillate and diluting the bottoms with a viscosity reducing liquid having a high gravity.

WILLIAM A. GRUSE. 

